Struct parquet::arrow::arrow_reader::RowSelection

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pub struct RowSelection { /* private fields */ }
Expand description

RowSelection allows selecting or skipping a provided number of rows when scanning the parquet file.

This is applied prior to reading column data, and can therefore be used to skip IO to fetch data into memory

A typical use-case would be using the PageIndex to filter out rows that don’t satisfy a predicate

§Example

use parquet::arrow::arrow_reader::{RowSelection, RowSelector};

let selectors = vec![
    RowSelector::skip(5),
    RowSelector::select(5),
    RowSelector::select(5),
    RowSelector::skip(5),
];

// Creating a selection will combine adjacent selectors
let selection: RowSelection = selectors.into();

let expected = vec![
    RowSelector::skip(5),
    RowSelector::select(10),
    RowSelector::skip(5),
];

let actual: Vec<RowSelector> = selection.into();
assert_eq!(actual, expected);

A RowSelection maintains the following invariants:

Implementations§

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impl RowSelection

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pub fn from_filters(filters: &[BooleanArray]) -> Self

Creates a RowSelection from a slice of BooleanArray

§Panic

Panics if any of the BooleanArray contain nulls

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pub fn scan_ranges(&self, page_locations: &[PageLocation]) -> Vec<Range<usize>>

Given an offset index, return the byte ranges for all data pages selected by self

This is useful for determining what byte ranges to fetch from underlying storage

Note: this method does not make any effort to combine consecutive ranges, nor coalesce ranges that are close together. This is instead delegated to the IO subsystem to optimise, e.g. ObjectStore::get_ranges

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pub fn split_off(&mut self, row_count: usize) -> Self

Splits off the first row_count from this RowSelection

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pub fn and_then(&self, other: &Self) -> Self

returns a RowSelection representing rows that are selected in both input RowSelections.

This is equivalent to the logical AND / conjunction of the two selections.

§Example

If N means the row is not selected, and Y means it is selected:

self:     NNNNNNNNNNNNYYYYYYYYYYYYYYYYYYYYYYNNNYYYYY
other:                YYYYYNNNNYYYYYYYYYYYYY   YYNNN

returned: NNNNNNNNNNNNYYYYYNNNNYYYYYYYYYYYYYNNNYYNNN
§Panics

Panics if other does not have a length equal to the number of rows selected by this RowSelection

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pub fn intersection(&self, other: &Self) -> Self

Compute the intersection of two RowSelection For example: self: NNYYYYNNYYNYN other: NYNNNNNNY

returned: NNNNNNNNYYNYN

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pub fn selects_any(&self) -> bool

Returns true if this RowSelection selects any rows

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pub fn iter(&self) -> impl Iterator<Item = &RowSelector>

Returns an iterator over the RowSelectors for this RowSelection.

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pub fn row_count(&self) -> usize

Returns the number of selected rows

Trait Implementations§

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impl Clone for RowSelection

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fn clone(&self) -> RowSelection

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for RowSelection

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Default for RowSelection

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fn default() -> RowSelection

Returns the “default value” for a type. Read more
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impl From<RowSelection> for Vec<RowSelector>

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fn from(r: RowSelection) -> Self

Converts to this type from the input type.
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impl From<RowSelection> for VecDeque<RowSelector>

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fn from(r: RowSelection) -> Self

Converts to this type from the input type.
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impl From<Vec<RowSelector>> for RowSelection

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fn from(selectors: Vec<RowSelector>) -> Self

Converts to this type from the input type.
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impl FromIterator<RowSelector> for RowSelection

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fn from_iter<T: IntoIterator<Item = RowSelector>>(iter: T) -> Self

Creates a value from an iterator. Read more
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impl PartialEq for RowSelection

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fn eq(&self, other: &RowSelection) -> bool

Tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl Eq for RowSelection

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impl StructuralPartialEq for RowSelection

Auto Trait Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> Allocation for T
where T: RefUnwindSafe + Send + Sync,